Switch for electric heaters



' Jan. 10, 1933. L, THOMAS 1,893,568

SWITCH FOR ELECTRIC HEATERS Filed Feb, 28, 192 73 Sheets$heet 1 7 auucwtoz Zazzrerme H 720mm Jan. 10, 1933. H. THOMAS 1,893,568

SWITCH FOR ELECTRIC HEATERS Filed Feb. 28. 1927 2 Sheets-Sheet 2 i W m Wezce 15. 730mm attoznew hill.

Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE LAURENCE H. THOMAS, DETROIT, MICHIGAN, ASSIGNOR TO AMERICAN ELECTRICAL HEATER COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MIGHIG-Ml' SWITCH FOR ELECTRIC HEATERS Application filed February 28, 1927.- Serial No. WLGGB.

The invention relates to improvements in electric switches and more particularly refers to thermostatically operated switches adapted for use on electric irons..

One of the objects of the invention is to provide a switch mechanism in which the contacting points are separated by an exceptionally fast movement to avoid arcing. Another object is to provide an arrangement whereby the contacts are held in contact with a ositive pressure until the moment of the. tripping action. A further object is to provide a construction wherein the contacting member may be tripped with very slight effort in order to actuate the lever in its opening movement and at the same time provide means for applying sufficient pressure to the contact member at the moment the break is made to insure positive action even though the contacts are sticky A still further object is to provide a construction free fromsliding contacts and so constructed as to be practically operative at relatively high temperatures.

Another object is to provide a combined manually operable and thermostatically operable switch arranged in a convenient location on the iron whereby it may readily be operated by the hand which is grasping the iron handle. Other objects are the provision of means for adjusting the thermostatic connection to automatically open the switch at different predetermined temperatures and to simplify the switch construction by employing a relatively small number of parts.

These and other objects are obtained in thenovel construction hereinafter described and illustrated in the accompanying drawings, wherein Figure l is a perspective view of an electric iron equipped with the new switch;

Figure 2 is a longitudinal section through the iron and switch;

I Figure 3 is a top plan View of the switch unit showing also a portion of the iron; Figure 4 is a bottom plan view thereof;

Figure 5 is a longitudinal section on the line 55 of Figure 3;

Figure 6 is a diagrammatic view illustrating the arrangement of the levers and resilient connection;

Figure 7 is a perspective view of the switchthe actuating lever movable about the fulcrum l3 and extending outwardly in the opposite direction from the contact lever 10. His a coil spring attached to the lever 12 at 15' and to the lever 10 at 16 and arranged to be under an initial tension. The contacts on the lever '10 are indicated generally at l? and are arranged to cooperate with stationary contacts 18. The actuating lever 12 is provided with a suitable handle 19 for moving the same to opposite positions of adjustment against the stops 20 and 21.

The tulcrums 11 and 13 are slightly ofiset although arranged adjacent each other and the relationship of the parts is such that when the actuating lever 12 is in the right-hand position-that is, contacting with the stop 2l,the center line of the spring 14 is on the right-hand side of both fulcrums, thereby causing the contact lever 10 to be resiliently held in its right-hand position by reason of the spring tension. The center line of the spring, or, in other words, the line of action thereof, is represented by the numeral 22 and the arrangement is preferably such that when lever 12 is in right-hand position this line of 1 4 of the actuating lever by reason of the spring tension the contact lever 10 still remains in its right-hand position and the contacts are held in engagement by the tension of the will spring 14: since the line of action of the spring is still on the right-hand side of the. fulcrum 11. When the actuating lever has travelled a predetermined distance, namely until the line of action reaches the fulcrum 11, the spring action on the contact lever 10 is applied to the opposite side of said lever and the lever quickly moves to its left-hand position, thus breaking the contact. The quick action of the contact lever is due to the momentum of the actuating lever at the moment when the reversal in spring pressure takes place, since this momentum insures that the eflective leverage of the spring on the contact lever will be quickly increased as soon as breaking of the contacts is started. When the actuating lever is in its left-hand position, the line of action of'the spring is at the left of both fulcrums and both levers are therefore held in their left-hand positions.

The closing of the switch is eifected by manually moving the actuating lever from the left-hand to the right-hand positions and the contact lever 10 is moved when the line of action of the spring crosses the fulcrum 11, but the actuating lever is not held in its righthand position until after the line of action also crosses the fulcrum 13. The release of the actuating lever may be effected either manually through the handle 19 or automatically by means of a thermostat hereinafter more fully described.

Referring now more specifically to the construction illustrated in Figures 3 to 5, 23 represents the base or frame of the switch having the upturned end portions 24 and the laterally bent fianges 25. 26 is a bracket secured to the frame intermediate the ends 24 and provided with the V-shaped slots 27 and 28 arranged in alignment with corresponding slots 27 a and 28 in the frame member. These slots form the fulcrums for the respective levers. The contact lever 10 consists of a flat stamping 29 having laterally projecting ears 30 adapted to engage the V slots 27 and 27 The stamping is slotted at 31 for receiving the coil spring 14, which latter is suitably attached at 16. The stamping has secured thereto a strip 33 of insulating material, such as mica, on which is arranged metallic bracket 34 carrying contact disks 35 at opposite ends thereof.

The cooperating stationary contacts indicated generally by the reference character 18 in Figure 6 may be mounted on the frame in any suitable manner to provide the necessary insulation, but as shown. the arrangement comprises a pair of U-shaped metallic arms 36 and 37 which respectively carry the contact disks 38 and 39. The arms are secured to the frame in spaced relation by means of a clamping plate 40 and screw 41, there being.

- suitable insulation between the several metallic elements. Thus the switch arrangement .as shown provides a metallic bridge on the contact lever 10, which when engaging operating the actuating lever may be of various constructions, but as shown it comprises a bi-metallic strip 47 preferably formed of invar and Monel metal. The strip is secured by a bracket 48 to the under side of the frame 23, the bracket being secured by the screws 49 and the thermostatic strip riveted to the bracket at 50. 51 is an adjusting set screw threadedly engaging the bracket and bearing against thethermostatic strip. The free end of the thermostatic strip has a laterally projecting portion 52 projecting through aslot 53 in the frame 23 and arranged to contact with the actuating lever 12. The projection 52 thus forms one stop for the actuating lever 12, while the other stop 20 is formed by an upstanding strip secured to the frame. 54 is another stop' projecting from the frame 23 arranged to limit the movement of the contact lever 10.

The switch unit as above described is preferably mounted on the .casing 55 of the electric iron directly beneath the handle 56. Thus the casing is provided with an aperture 57 permitting the lower portion of the frame to extend within the casing and exposing the thermostatic strip to direct radiation from the heating element arranged in the bottom portion of the electric iron. The frame is secured to the casing by set screws 58 extending through the flanges 25 of the frame while the terminal arms 36 and 37 are secured to the respective terminals 59 and 60 leading to the circuit of the electric iron. 'The iron is preferably provided with a cap plate 61 having a slot 62 therein for receiving the shank of the handle 19 and is also provided with a second slot 63 a regulating arm 64. The arm 64 is attached to the adjusting screw 51 and serves to regulate the initial adjustment of the thermostat so that it will trip the lever 12 at the predetermined temperature.

The heating element 65 has one terminal connected by the outstanding conductor 66 to the terminal rod 67. The other end of'the heating element is connected at 68 to the insulated conductor69 leading to the terminal 60. The terminal 59 is also connected to an insulated conductor 7 0 leading to the other terminal pin 71. Thus the circuit through the heating element is completed through the metallic bracket 34 when the movable contact disks 35 engage the stationary contact disks 38 and 39.

through which pro ects v What I claim as my invention is:

1. In a switch mechanism, the combination of a contact lever and an actuating lever fulcrumed at offset points, a contact with which said contact lever engages, resilient means connecting said levers and normally holding said contact lever in engagement with said contact when the actuating lever is in one extreme osition, the fulcrums of said levers being 0 set in such relationship that the movement of said actuating lever from said extreme position moves the line of action of said resilient means first across the fulcrum of said actuating lever and then across the fulcrum of the contact lever, and the thermostatically operated means for moving said actuating lever to the point where said line of action crosses the fulcrum thereof.

2. In a switch, the combination of a contact lever and an actuating lever respectively fulcrumed at non-concentric points, a single spring connecting both of said levers and arranged to permit the line of action of the spring to be disposed alternatively on opposite sides of both of said fulcrums for successively operating the contact and actuating levers aforesaid, and a thermostatic element engaging said actuating lever and adapted to move the line of action of said spring to a position between said fulcrums.

3. In a switch, the combination with a contact lever adapted to make and break an electrical contact, manually operable means for actuating said lever, means for resilientl maintaining said lever in closed posit on, thermostatically operated means for tripping said resilient means, whereby said lever is automatically moved to open position, and means for adjusting said thermostatic means to tri said resilient means when sub]ected to diliiarent temperatures.

4. In a switch mechanism, the combination of a contact lever, an actuating lever, means for urging said contact lever alternatively in op osite directions when sald actuating lever 15 respectively on opposite sides of a predetermined position and for urging said actuating lever alternatively 1n opposlte directions when said actuating lever is respectively on opposite sides of a second predetermined position, manually operable means for operating said actuating lever and temperature responsive means for automatically moving said actuating lever in one direction. a

5. In a switch, the combination of an actuating lever and a contact lever respectively fulcrumed at ofiset points upon a support, a contact with which said contact lever engages, resilient means connecting said levers and normally holding said contact lever in engagement with the contact when the actuating lever is in one position, the fulcrums aforesaid of the levers being offset in such relationship that movement of the actuating lever from the aforesaid position of the same causes the line of action of the resilient means to move first across the fulcrum of said actuating lever and then across the fulcrum of the contact lever, and temperature responsive means for operating the actuating lever to position the line of action of the resilient means between the fulcrums aforesaid whereby continued movement of the actuating lever to move the line of action of the resilient means across the fulcrum of said contact lever is accomplished automatically and qluickly.

6. n a switch, the combination of a contact lever and an actuating lever having the adjacent ends fulcrumed upon a support in lateral spaced relation to each other, resilient means connecting the opposite end portions of the actuating lever and contact lever normally holding the contact lever in operative position and operable upon movement of the actuating lever to position the line of action of the resilient means between the fulcrums aforesaid for quickly moving the actuating lever to move the line of action of said resilient means across the fulcrum of the contact lever whereby the latter is snapped out of operative position, and temperature responsive means for effecting initial movement of said actuating lever.

In testimony whereof I affix my signature.

LAURENCE H. THOMAS. 

